This invention relates to a metal railing formed of sections, the sections comprising a closed or divided handrail adapted to receive a steel cable; at least one lower girder; and pinned filler bars supported at the inside of the upper wall of the handrail and at an inner wall of the lower girder. The railing sections are adapted to be supported movably at their ends by a pair of coupler posts, or by a coupler post and an end post. The center of the section is held by a center post. The sections preferably are fabricated substantially of light metal, such as aluminum.
German Pat. No. 1,003,937 discloses a railing structure, particularly for stairs, which consists of at least one hollow support section, a handrail detachably fastened thereto and, preferably, posts and filler bars. The posts and filler bars engage or reach into the support section and specifically extend through the bottom side of the supporting section. If an upper and a lower supporting section are used, for instance, the posts also extend through the lower supporting section. The upper supporting section and the lower supporting section are preferably of identical construction and configuration. However, the downwardly facing side of the bottom section is open, contrary to the corresponding downwardly facing side of the upper supporting section.
It is an essential feature of the structure of said German Pat. No. 1,003,937 that the posts and filler bars are connected to the two support sections, in a manner known per se, by pins which are inserted into transverse holes in the ends of the posts and filler bars, the pins being guided in lengthwise slots into inner surfaces of the supporting sections which face each other.
The posts and the filler bars were thereby secured against axial displacement as well as against rotation relative to each other.
Difficulties have been encountered in such railings in inserting the individual pins into the transverse holes of the filler bars, and in truly tightening them in the supporting sections. Railings of this type therefore had a tendency to develop rattling noises in the course of time and were expensive to install.
Modifications of this concept, particularly for the design of ladders, among other things, employ continuous rods instead of individual pins in the rungs. In such structures elastic deformation of the walls facing the rungs of the longitudinal beams was tolerated. As in the case of a railing, deformation of these walls is the same as deformations of the surfaces of the handrail and of the lower girder, which surfaces face each other. However, such deformations cannot be tolerated in the interest of preserving the possibility of a freely adaptable, simple installation of different railing units in sections of the total length of a railing structure. The deformation to be expected cannot be predetermined exactly, and imponderables in the manufacture and the material cannot be adequately eliminated in said known structure.
Railings required for the purpose of traffic safety, particularly for securing bridges, streets and railroad rights-of-way must therefore be designed according to other principles.
Thus, if a vehicle strikes the railing it is very important with respect to the extent of the damage, how large the bending moment of inertia is if the load is directed at the height of the railing girder or the handrail, and how large the torsion moment of inertia of the girders is, if the load is directed at the height of the filler bars in order to enable deflection of the load forces safely into the posts.
For this reason, special hollow sections were made as so called "handrail" sections, i.e. as railing girders, which are fabricated from light metal and generally exhibit optimum static values. In individual cases, steel cables are placed in these sections. The steel cables are clamped to the individual posts and serve as a safety reserve in the event that the limits of the railing are exceeded, even though the material is optimally employed. By such a time a large part of the motion energy is then already converted.